1. Field of the Invention
The present invention relates to water dispersible compounds, which contain alkoxysilane groups and are substantially free from isocyanate groups, and to their use in aqueous, one-component coating compositions.
2. Description of the Prior Art
Alkoxysilanes containing amino groups are key components for linking conventional polymer chemistry with silicone chemistry. The alkoxysilane groups crosslink by "silane polycondensation" in the presence of moisture, and the amino groups can be incorporated into polymers, such as polyurethanes and polyureas.
U.S. Pat. No. 5,364,955 discloses that by initially reacting amino-functional silanes with maleic or fumaric acid esters to form secondary amino groups (i.e., aspartates), it is then possible to react these aspartates with NCO prepolymers without encountering incompatibility, inhomogeneity or extremely high viscosities in the reaction products. Copending application, U.S. Ser. No. 08/814,561, discloses the reaction of aspartates with monomeric polyisocyanates or polyisocyanate adducts to form compounds containing urea and alkoxysilane groups.
One of the uses for these compounds is to mix them with water either alone or with other compounds containing alkoxysilane groups to form stable sol-gel formulations. In these formulations water is required to hydrolyze the silyl ether groups to form hydroxy silanes. The terminal Si--OH groups can then be crosslinked into a polysiloxane network through a condensation reaction to form Si--O--Si bonds. However, when it is attempted to mix the compounds described in the preceding copending application with water, stable dispersions are not formed.
It is an object of the present invention to provide compounds containing alkoxysilane groups, which 1) may be mixed with water to form stable water-in-oil or oil-in-water dispersions and 2) cure to form smooth, clear coatings. It is an additional object of the present invention to provide hydrophilic compounds containing alkoxysilane groups that can be cured by silane polycondensation to form coatings, sealants, and adhesives.
These objects may be achieved with the water dispersible compounds containing alkoxysilane groups according to the present invention described hereinafter. These compounds may be prepared by reacting a polyisocyanate component with compounds containing secondary amino groups and alkoxysilane groups.